An organic EL light-emitting device having a plurality of electrode layers and a light-emitting layer disposed therebetween to generate electrical light emission has been studied for its use as a display device that can be a substitute for a liquid crystal cell. The organic EL light-emitting device has also been studied as to its use for a surface light source device such as planar lighting and a backlight for a liquid crystal display device, taking advantages of its characteristics such as high light-emitting efficiency, low-voltage drive, lightweight, and low cost.
When the organic EL light-emitting device is used as a light source of a surface light source device, there is a demand for extracting light in a useful state with high efficiency from an element. For example, although the light-emitting layer of the organic EL light-emitting device has high light-emitting efficiency, the layers constituting the device may incur a large amount of loss of light while the light is passing through the layer before the light emission, depending on conditions such as a refractive index difference between the layers. Therefore, there is a demand for keeping the loss of light as small as possible.
As a method for increasing light extraction efficiency, for example, provision of many concave portions or convex portions on a light-emitting surface of the organic EL light-emitting device has been known. For example, Patent Literature 1 proposes that pyramidal concave portions are formed on a light-emitting surface of an organic EL light-emitting device, by which improvement in the light extraction efficiency is expected.